1. Technical Field
Example embodiments generally relate to a pressure adjuster, a fixing device, and an image forming apparatus, and more particularly, to a pressure adjuster for changing pressure between a plurality of opposed bodies and a fixing device and an image forming apparatus incorporating the pressure adjuster.
2. Background Art
Related-art image forming apparatuses, such as copiers, facsimile machines, printers, or multifunction printers having two or more of copying, printing, scanning, facsimile, plotter, and other functions, typically form an image on a recording medium according to image data. Thus, for example, a charger uniformly charges a surface of a photoconductor; an optical writer emits a light beam onto the charged surface of the photoconductor to form an electrostatic latent image on the photoconductor according to the image data; a development device supplies toner to the electrostatic latent image formed on the photoconductor to render the electrostatic latent image visible as a toner image; the toner image is directly transferred from the photoconductor onto a recording medium or is indirectly transferred from the photoconductor onto a recording medium via an intermediate transfer belt; finally, a fixing device applies heat and pressure to the recording medium bearing the toner image to fix the toner image on the recording medium, thus forming the image on the recording medium.
Such image forming apparatus may incorporate a pair of opposed bodies, such as a pair of rollers, pressed against each other. For example, the fixing device incorporated in the image forming apparatus may include a fixing rotary body and a pressing rotary body pressed against the fixing rotary body. A spring biases the pressing rotary body against the fixing rotary body to form a fixing nip therebetween. As the recording medium bearing the toner image is conveyed through the fixing nip, the fixing rotary body and the pressing rotary body apply heat and pressure to the recording medium, thus melting and fixing the toner image on the recording medium.
The fixing device may further include a mechanism to decrease pressure between the fixing rotary body and the pressing rotary body to facilitate removal of the recording medium accidentally jammed between the fixing rotary body and the pressing rotary body or to prevent creeping of the fixing rotary body and the pressing rotary body which may arise after the pressing rotary body is pressed against the fixing rotary body for an extended period of time. For example, JP-2009-139682-A discloses a cam that rotates to decrease pressure exerted by a pressure roller biased by a spring. However, the cam may produce noise as it rotates.